Dyke complex of the East Pacific Rise exposed in the walls of Hess Deep and the structure of the upper oceanic crust
Dyke complex of the East Pacific Rise exposed in the walls of Hess Deep and the structure of the upper oceanic crust
复制标题
赫斯深海壁中暴露的东太平洋隆起的岩脉复合体和上洋壳的结构
DOI：
10.1016/0012-821x(92)90173-s
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发表时间：
1992
影响因子：
5.3
通讯作者：
N. Blum
中科院分区：
文献类型：
--
作者：
J. Francheteau;R. Armijo;J. Cheminée;R. Hékinian;P. Lonsdale;N. Blum
在用潜水鹦鹉螺号在赫斯深海壁进行潜水期间，对位于东太平洋海隆轴部的最上层地壳的喷出和侵入单元进行了详细观察。在四个相距甚远的地点，发现了相同的层序：上部较薄（100-200米）的喷出岩（枕状熔岩）单元，下面是厚度不等（50-500米，平均200米）的混合带，在混合带中发现了喷出岩和侵入岩以及可能代表岩床的块状近水平层。混合带本身位于席状岩墙单元之下，厚度可达1200 m，那里的堤坝近乎垂直（即不倾斜）和平行于东太平洋隆起组构。这个序列可能是一个一般特征的中快速-扩展地壳，因为它类似于在哥斯达黎加裂谷504 B孔中观察到的，并且与来自地震的上洋壳图像一致。东太平洋海隆轴上的实验岩墙的厚度是一个很好的测量深度的顶部轴向岩浆房。观测剖面为东太平洋隆起地壳提供了急需的“地面实况”。熔岩序列的厚度和第2层的总厚度（最多1400米）似乎在以前的洋壳研究中被高估了。
Detailed observations have been made of the extrusive and intrusive units of the uppermost crust emplaced at the axis of the East Pacific Rise during dives conducted with the submersibleNautileon the walls of Hess Deep. At four widely separated locations, the same sequence was found: an upper, thin (100–200 m) unit of extrusives (pillow lavas) underlain by a mixed zone of variable thickness (50–500 m, averaging 200 m) where extrusives are found and intrusives and massive subhorizontal layers which may represent sills. The mixed zone itself is underlain by a sheeted dyke unit, that may be up to 1200 m thick, where dykes are subvertical (i.e. untilted) and parallel to the East Pacific Rise fabric.This sequence may be a general feature of medium to fast-spreading crust because it is similar to that observed in Hole 504B of the Costa Rica Rift and is consistent with images of the upper oceanic crust derived from seismic experiments on the axis of the East Pacific Rise. Dyke thickness is a good measure of the depth to the roof of the axial magma chamber. The observed sections provide much needed “ground-truth” for East Pacific Rise crust. The thickness of the lava sequence and the overall thickness of Layer 2 (at most 1400 m) appear to have been overestimated in previous studies of the oceanic crust.